Compression encoding means a series of signal processing technologies for transmitting digitized information through a communication line or storing the information in a form suitable for a storage medium. Media, such as a picture, an image and voice, may be the subject of compression encoding. In particular, a technology performing compression encoding on an image is called video image compression.
Next-generation video content will have features of high spatial resolution, a high frame rate, and high dimensionality of scene representation. Processing such content will result in a tremendous increase in terms of memory storage, a memory access rate, and processing power. Therefore, there is a need to design a coding tool for processing next-generation video content more efficiently.
In particular, many image processing and compressing schemes have adapted separable transforms. For example, a Discrete Cosine Transform (DCT) provides good approximation to a Karhunen-Loeve transform (KLT) in response to a high inter pixel correlation, and it is used widely due to low complexity. Regardless of use of separable transforms, natural image compression has very different statistical properties, so better compression may be performed only by means of a complex transform applicable to variable statistical properties of signal blocks.
Actual implementations have been so far focused on separable approximation of such transforms in order to provide a low-complex reasonable coding gain. For example, a mode-dependent transform scheme is designed such that a separable KLT reduces complexity of a non-separable KLT for each mode. In another example, an asymmetric discrete sine transform (ADST) is integrated into a hybrid DCT/ADST scheme and designing a separable sparse orthonormal transform and the like has been considered.